Electromagnetic relays



June 16, 1959' R. E. H. CARPENTER 2,8

ELECTROMAGNETIC RELAYS Filed Aug. 19, 1955 I 2 Sheets-Sheet 2 47 1y 1/,21K f5 :11 i if 54 7- Z 3; AP 54 w /7 x f2 :1 I v 200 9% I 17 M z/ I 4d20 m A I Inventor Rumm- E. H- GAR EM ByWB.

Attorney United States Patent 2,8?1300 ELECTROMAGNETIC RELAYS RupertEvan Howard Carpenter, South Croydon, England Application August 19,1955, Serial No. 529,467

Claims priority, application Great Britain August 27, 1954 19 Claims.(Cl. 317--198) The pivoting and positioning of the armature inelectromagnetic relays have always been major problems in the design ofsuch devices, and especially so in the case of polarised relaysemploying moving iron armatures working in small air gaps.

Since ordinary types of pivot, such as are used in clocks, are generallyunsatisfactory, being expensive to make well and being liable either tobind or to develop shake, the armature in many forms of relay is mountedfor rocking movement on a spring or springs. Such springs (or spring)act on the armature with a mechanical force which tends to hold thearmature in a position of mechanically stable equilibrium between thepolar faces of the air gap in which the armature is mounted, and thismechanical force imparts to the armature a positive stiffness. Themagnetic forces acting on the armature, however, tend to move it out ofany position of magnetically unstable equilibrium towards one of thepolar faces. Such magnetic forces thus operate against the mechanicalforces and impart to the armature and its associated magnetic circuitwhat may be regarded as a negative stiffness. The total stiffness, thatis to say the algebraic sum of this negative stiffness and the positivestiffness, governs (together with the positions of the contacts of therelay), the degree and type of stability of the armature. Thus in asummetrically arranged relay with symmetrically dis- .posed contacts,when the mechanical stiffness is greater than the magnetic stiffness sothat the total stiffness is positive, the relay is of the centre-stabletype, whilst when the mechanical stiffness is smaller so that the totalstiffness is negative, a both-sides-stable relay is obtained.

Unless the armature is mounted like a reed, howeverand such a design isgenerally useless when the instrument has to be mobile and subject toconsiderable acceleration's-the design of such springs presentsconsiderable difficulties. This is because the mechanical force whichthe springs apply to the armature must be of the correct value toproduce the required degree and type of stability, whilst at the sametime they must be stiif enough to determine the pivotal axis of thearmature so that movements of the armature in any but the desireddirections are prevented. Moreover, the alfixing of these springs to therelay structure so that the armature is set as accurately as possiblesymmetrically with respect to the polar faces of the air gap isdifiicult, especially when the effects of temperature variation and ofcreep in the springs or their supports comes into question, and thesedifiiculties are enhanced when the relay has to operate under highacceleration.

According to the present invention, the armature is journalled in anelastomer member or members having a torsional stiffness which is smallcompared with the magnetic negative stiffness of the armature and itsassociated magnetic circuit, but having a sufficiently large stiffnesstransverse to the pivotal axis of the armature to determine the positionof that axis. Thus this elastomer has no significant effect incontrolling the rocking movement of the armature whilst keeping thepivotal axis of the lat- 2,891,206 Patented June 16, 1959 ter inposition. Since the torsional stilfness of the elastomer is smallcompared with that of the springs used hitherto, hysteresis or creep isof negligible effect.

The small torsional force exerted by the elastomer may be the onlymechanical force acting on the armature, in which case movements of thearmature are controlled almost exclusively by the magnetic forces. Arelay having such an arrangement will have only a low sensitivity sincea large number of ampere-turns will be needed to overcome the largenegative stiffness of the armature and its associated magnetic circuit.Preferably therefore, a resilient element or elements are arranged toact on the armature to provide it with a mechanical stiffness whichopposes the magnetic negative stiffness. By thus decreasing the totalstiffness of the armature, the sensitivity of the relay is increased.

In the preferred form of a relay constructed according to the invention,the pivot of the armature comprises two coaxial pins projecting fromeither side of the armature, each being surrounded by an elastomersleeve having an adjustable position in the relay. Such pins and sleevesmay be conical in form so that by adjusting the end pressure axially thetorsional stiffness and the stiffness transverse to the pivotal axis maybe altered. Preferably however, such pins and sleeves are cylindricaland each sleeve is held under compression by the inner cylindricalsurface of a corresponding rigid holder which is provided with a flangeat its outer end and which has such outer dimensions that it may bemoved within a corresponding opening in a fixed part of the relay inwhich the holder is carried so as to enable the position of the pivotalaxis to be adjusted, clamping means being provided to enable the flangeof the holder, and thus the pivotal axis of the armature, to be fixed inposition.

A relay constructed in accordance with the invention together with amodified pivoting arrangement for this relay will now be described, byway of example, with reference to the accompanying drawings in which:

Figure 1 is an elevation of the relay;

Figure 2 is an elevation of the relay looking from the left of Figure 1Figure 3 is a section of the pivoting arrangement of the armature;

Figure 4 is an elevation of this arrangement looking from the left ofFigure 3;

Figure 5 is a plan of the relay; and

Figure 6 is .a section of the modified pivoting arrangement.

The relay illustrated and described below is the subject of theco-pending patent application, Serial No. 520,853 filed July 8, 1955,now Patent No. 2,816,976.

Referring first of all to Figures 1 and 2, the signals magneticstructure includes two signal coils 1 and 2 .arranged side by side andhaving corresponding Mumetal cores 3 and 4 which are joined together attheir lower ends. These cores extend upwards outside .the coils and areconnected to corresponding fiat parallel Mumetal plates 5 and 6 whichconstitute the pole faces between which the armature of the relay rocks.The plates 5 and 6 are maintained a fixed distance apart by two up rightbrass bars 7 which are arranged between the plates 5 and 6 along theiradjacent vertical sides. The faces of the bars in contact with theplates are accurately finished so that the distance between the platesis accurately determined. The lower ends of the plates and the bars andthe extension of the cores 3 and 4 are held in position by two bolts 8,whilst two fuither bolts 9 hold in position the upper ends of the platesand the bars and also two brackets 10, upon the upper surface of whichis mounted an insulating disc 11 of Mycaleir,

tense pressure. The coeflicient of expansion of Mycalex is approximatelythe same as that of Mumetal and thus prevents unduly large strains beingset up on change of temperature. The disc 11 carries the contactarrangement of the relay. A bottom plate 12 is fixed across the bottomof plates and 6 and the bars 7 so that the armature is completelyenclosed within the box made up of this bottom plate 12, the disc 11,the bars 7 and the plates 5 and 6. This particular design of relay thusprevents magnetic or other particles from penetrating into regions nearthe armature.

The armature which is pivoted between the centres of the two brass bars7 as described below, consists of a permanent magnet of rectangularcross-section and two similar radiometal end pieces 16 secured (as byone of the methods referred to in the above-mentioned copendingapplication) to the magnet 15 at its poles, that is at the top andbottom.

The operation of the armature of this relay, and the advantages whichfollow from its construction are both given in detail in theabove-mentioned co-pending application, and so will not be describedhere.

Referring now to Figures 3 and 4, two cylindrical pins 17 (only one ofwhich is shown, the other being similar), having a diameter of 0.052inch, are fixed to, and project from, the sides of the magnet 15 andeach is held within a corresponding cylindrical sleeve 18 made of amechanically, thermally and chemically stable elastomer of the siliconetype, such as one of those sold under the registered trademarkSilastomer. Each sleeve 18, in its unstressed condition, has an innerdiameter of 0.041 inch and an outer diameter of 0.082 inch and is thuscompressed by a rigid metal cylindrical holder 19 of inner diameter0.078 inch within which the sleeve is held. During a rocking movement ofthe armature the outer surface of the sleeve 18 remains stationary,whilst its inner surface moves with the pin. The compressed elastomerhas only a small torsional stiffness compared with the magnetic negativestiffness of the armature and its associated magnetic circuit whilst ithas a sufliciently large stiflness transverse to the pivotal axis of thearmature to determine the position of that axis. By compressing theelastomer more in a radial direction, that is transverse to the pivotalaxis, an increased transverse or lateral stiffness may be obtainedwithout a proportional increase in the torsional stifiness and thuswithout making this torsional stiffness of the same order as, or largerthan, the magnetic negative stifiness. Thus it has been found that byincreasing the lateral compression of one particular elastomer sleeve sothat its transverse stiffness is increased by a factor of three, itstorsional stiffness increases by a factor of only about a half.

In order to prevent the sleeve 18 from slipping parallel to the axis ofthe pin 17, the sleeve is bonded to either the pin 17 or the holder 19or both. In another arrangement, shown in Figure 6, the pin 17 isscrew-threaded at its outer end and thereby carries a nut 20a whichbears on the outer end of the sleeve 18 and thus main tains the sleevein position. In yet another arrangement (not shown) the sleeve 18 isprovided with a flange which bears against one end of the holder 19 andthus positively prevents axial movement of the sleeve beyond a certainpoint.

Each holder 19 is formed at its outer end with an annular flange 20, andthe cylindrical part of the holder lies within a corresponding bore 21formed in one of the brass bars which thus serve both to determine thegap between the plates 5 and 6 and to support the armature pivotingsystem. The outer diameter of each holder 19 is smaller than that of itsbore 21 so that, until the holders 19 are clamped in position, thearmature may be adjusted with respect to the plates 5 and 6. Each of theflanges 20 lies in a corresponding shallow groove 22 formed across thebar 7 and the sides of the two slides over the friction surface.

plates 5 and 6, this groove 22 lying within a deeper and longer portion23 also cut across the bar 7 and the sides of the plates 5 and 6. Thegroove 22 is made only just slightly wider than the outer diameter ofthe circular flange 20, so that the pivot of the armature issubstantially fixed in a vertical direction but, owing to the loose fitof the holder 19 in its bore 21 it can be moved at right angles to thisdirection so that the armature may be adjusted with respect to theplates 5 and 6. During the assembly of the relay, spacing shims (notshown) are temporarily inserted between the armature and these plates 5and 6 the shims having a thickness to correspond to the required airgaps and pivot 17 of the armature is then fixed by a brass plate 24which fits into the cut-away portion 23 and which is fixed by screws 24aonto the bar. Thus the centre portion of this plate 24, which is formedwith a small aperture 25 through which the pin 17 of the armature maypass presses against the flange 20 to maintain it in correct position.In the modified pivoting arrangement shown in Figure 6, a large aperture25a is provided to accommodate the nut 20a, the part of the plate 24surrounding this aperture 25a again pressing against the flange 20 tomaintain it in its correct position.

One of the pins 17 is longer than the other (see Figure l) and passesthrough the corresponding aperture 25 (or 25a). Thus a long uprightmagnetic strip 28, fixed to this longer pin 17 and extending from nearthe top of the signals coils 12 to just above the disc 11 rocks to andfro with the pin 17 and the armature and thereby serves to convey therocking eifect of the armature to the contact making arrangement on thedisc 11. Lying on the strip 28, and held to it by its own flux is apermanent magnet in the form of a thin plate 29 which is pivoted freelyabout a cylindrical boss 30 formed on the outer surface of the strip 28.This thin plate 29 serves to produce an inertia damping effect onoscillations of the armature in the manner disclosed in my Britishpatent specification No. 673,867. In order to bring about operation ofthe contacts, the strip 28 is turned over at the top through a rightangle so as to form a horizontal platform on which is secured abarrel-shaped insulating bead 31 which then rocks in synchronism withthe armature.

Two cars 32 which are fixed to and depend from a spring arm 33 extendingat right angles to the direction of movement of the head 31 are spreadto engage the head 31 on opposite sides. This spring arm 33 thusconstitutes the resilient element which acts on the armature to provideit with a mechanical stiflness opposing the magnetic negative stiffness.

It can be seen that rocking of the head 31 causes the spring arm 33together with conducting studs 34 forming the moving relay contactswhich it carries near the ears, to move in one direction or the otherdepending upon the direction of rocking of the head 31. The sidecontacts with which the moving contacts 34 cooperate lie, of course, onopposite sides of the spring arm 33 and are arranged to provide a degreeof friction damping to reduce contact chatter and oscillation on impact,as explained in British patent specification No. 484,472. Thus each ofthese side contacts consists of a stud 35 mounted on a spring strip 36which is fixed at one end to a rigid backing bar 37 so that the strip 36and the bar 37 lie roughly parallel to, but spaced from, each other. Thefree end of the strip 36 and the nearby end of the bar 37 are benttowards the arm 33, and a plug 38 having a front face with a desiredfrictional characteristic is screwed through this bent part of thebacking bar so that the free end of the strip bears upon the frictionsurface. Now when one of the studs 34 makes contact with one of thestuds 35, the strip 36 is pushed towards the backing bar and at the sametime the free end of the strip The energy thus absorbed reduced anytendency to chatter or to oscillate of the studs. When the thin plate 29is employed thereby producing an inertia damping effect as previouslymentioned, the plugs 38 may be dispensed with.

Each backing bar is supported by a corresponding resilient strip 45connected at one end to the back of the bar and at the other end to anupright post 46 which is mounted on the disc 11. Each strip 45 is turnedthrough a right angle and so fixed to the post that the backing bar isapproximately parallel to one of the surfaces of the post 46, and sothat it causes an adjusting screw 47 which is screwed through the post46 to bear on the back of the backing member 37. Thus the positions ofthe studs 35 are controlled by these adjusting screws. I n

In order to enable the magnetic and mechanical dead centres of thecentral contact supporting structure to be brought into coincidence asexplained in my above-meritioned co-Periding application, the spring arm33 is anchored at its fixed end in an upright post 50 mounted at theapex of a triangular horizontal plate 51 which is adjustably fitted ontothe disc 11. This adjustable fitting is brought about by a hexagonal nut52 with a conical undersurface which acts as a pivot for the plate 51,and two screws 53 and 54 the shank portions of which are of smallerdiameter than that of the bores in the plate 51 through which they pass.Thus the whole plate 51 (carrying with it the spring arm 33 and thestuds 34) may be turned through a small angle about the nut 52 with asuitable tool, the plate then being locked in position by tightening thenut and the two screws.

I claim:

1. An electromagnetic relay, comprising a frame, a magnetic structuremounted on said frame and formed with a pole face, an armature spacedfrom said pole face by a working air-gap and defining with saidstructure a circuit for magnetic flux, said armature being mounted insaid frame so as to be movable about a pivotal axis to and from saidpole face, a signal winding linked with said circuit, bearing members onopposite sides of said armature and providing a pivotal support for saidarmature, said members including resilient means exerting upon saidarmature a pressure having at least components acting radially aroundsaid pivotal axis and tending to maintain said pivotal axis in a desiredposition, means adjustably mounting said bearing members relatively tosaid frame to permit adjustment transversely of said pivotal axis toalter the length of said air-gap, and clamping means for securing saidmembers to said frame to determine said pivotal axis permanently.

2. A relay according to claim 1 wherein the bearing members are taperedin opposite directions and cooperate with correspondingly taperedsurfaces on the armature, whereby axial movement of the armature issubstantially prevented.

3. A relay according to claim 1 comprising means producing a polarisingmagnetic flux across said working air gap giving to said armature anegative torsional stifiness about said pivotal axis, and furtherresilient means mounted between said armature and said frame andproviding for said armature a positive torsional stiffness about saidpivotal axis of much greater magnitude than the positive torsionalstiffness provided by the first-named resilient means.

4. A relay according to claim 1 wherein said magnetic structure includestwo parallel pole faces spaced apart and said armature is locatedbetween the parallel pole faces, said bearing members being adjustableto alter the lengths of the air gaps between the armature and the pairof pole faces, whereby the armature may be moved to a central positionbetween the pole pieces and parallel to them.

5. A relay according to claim 4 wherein said bearing members are taperedin opposite directions and cooperate with correspondingly taperedsurfaces on the armature, whereby axial movement of the armature issubstantially prevented.

6. A relay according to claim 1, said bearing members and said armaturehaving male and female parts, and said resilient means comprising anelastomer member confined between said parts.

7. A relay according to claim 6 wherein said elastomer members areformed of silicone.

8. A relay according to claim 6, said armature having male partscomprising two coaxial pins having cylindrical surfaces and secured toand projecting from opposite sides of the said armature, said femaleparts comprising bearing members having cylindrical openings receivingsaid pins and said elastomer members comprising sleeves confined withinsaid cylindrical openings and surrounding said pins. v

9. A relay according to claim 8, each of said bearing members comprisinga hollow sleeve constituting said female part and an annular flange oneach bearing sleeve constituting said adjustable means, said flangebeing secured to said frame by said clamping means and said frame beingformed with openings in which said sleeves of said bearing members areadjustably located.

10. A polarised electromagnetic relay comprising a frame, a magneticstructure mounted on said frame and formed with two facing pole faces,an armature located between said pole faces and defining with saidstructure circuits for magnetic flux, said armature being mounted uponsaid frame to be movable about a pivotal axis towards one of said polefaces and away from the other of said pole faces, means producing apolarising magnetic fluX between said pole faces and said armature, asignals winding linked with said circuits, bearing members on oppositesides of said armature and providing a pivotal support for saidarmature, said bearing members including resilient means exerting uponsaid armature a pressure having at least components acting radiallyaround said pivotal axis and tending to maintain said pivotal axis in adesired position, means adjustably mounting said bearing membersrelatively to said frame to permit adjustment transversely of saidpivotal axis to center said armature between said pole faces, andclamping means for securing said members to said frame to hold saidpivotal axis in adjusted position.

11. An electromagnetic device comprising a frame including a fixedmagnetic member, a magnetic member movable about a pivotal axisrelatively to said frame, male and female support members, the latter insurrounding relation to the former, one of said support members beingfixed to said movable member, movably engaging surfaces on the other ofsaid support members and on said frame permitting adjustment of saidother support member in a direction perpendicular to said pivotal axisto vary the relative positions of said fixed and movable magneticmembers, resilient means interconnecting the support members to exertpressure between them, said pressure having at least components actingradially around said pivotal axis and tending to maintain said axis infixed relation to said support members, and means for rigidly clampingsaid other support member to said frame.

12. A device according to claim 11, wherein said resilient means is anelastomer member compressed between said support members.

13. A device according to claim 12, wherein said elastomer member is asilicone elastomer.

14. A device according to claim 13, comprising further resilient meansproviding between said movable member and said frame a torsionalstiffness much greater than that provided by said elastomer member.

15. A device comprising a frame, a member movable about a pivotal axisrelatively to said frame, male and female support members, the latter insurrounding relation to the former, one of said support members beingfixed to said movable member, movably engaging surfaces on the other ofsaid support members and on said frame permitting adjustment of saidother support member in a direction perpendicular to said pivotal axis,elastomer members positioned between the support members to, exertpressure between them, said pressure having at least components actingradially around said pivotal axis and tending to maintain said axis infixed. relation to said support members, and means for rigidly clampingsaid other support member to said frame.

I 16. A device according to claim 15, wherein said elastomer members aresilicone elasto-mer.

17. A device according to claim 15, comprising resilient means providingbetween said movable member and said frame a torsional stiffness muchgreater than that provided by said elastomer members.

18. An electromagnetic relay, comprising a frame, a magnetic structuremounted on said frame and formed with a pole face, a signals windinglinked with said structure, an armature spaced from said pole face by aWork ing air-gap and mounted in said frame so as to be mov able about apivotal axis to and from said pole face, sup porting means on oppositesides of said armature to provide pivotal support for said armature insaid frame and to determine the position of said pivotal axis, each saidsupporting means comprising a male pivot member, a female pivot membersurrounding the male pivot member and resilient means exerting betweensaid members a pressure having at least components acting radiallyaround said pivotal axis and tending to maintain said pivotal axis in adesired position, one of said members and said frame having flatsurfaces engaging each other on a plane transversely of said pole face,said one member being adjustable to effect relative sliding of said engaging surfaces in a direction to alter the length of said air gap, andclamping means for clamping said one member to said frame with saidsurfaces in rigid engagement to determine the position of said pivotalaxis permanently.

19. An electromagnetic relay, comprising a frame, a magnetic structuremounted on said frame and formed With a pole face, an armature spacedfrom said pole face by a working air-gap and defining with saidstructure a circuit for magnetic flux, said armature being mounted insaid frame so as to be movable about a pivotal axis to and from saidpole face, a signal winding linked with said circuit, supporting meanson opposite sides of said armature to provide pivotal support for saidarmature in said frame and to determine the position of said pivotalaxis, each said supporting means comprising a male pivot member, afemale pivot member surrounding the male pivot member and resilientmeans exerting between said members a pressure having at leastcomponents acting radially around said pivotal axis and tending tomaintain said pivotal axis in a desired position, one of said membersand said frame having surfaces engaging each other over an area orientedto permit adjustment of said one member with respect to said frame byrelative sliding of said engaging surfaces in a direction to alter thelength of said air gap, and clamping means for clamping said one memberto said frame with said surfaces in rigid en'- gagement to determine theposition of said pivotal axis permanently.

References Cited in the file of this patent UNITED STATES PATENTS FranceJan. 30, 19 52

